The present application is related to one contemporaneously and one previously filed U.S. patent applications having the same title, the same inventors and the same assignee with the invention.
1. Field of the Invention
The present invention relates to an antenna, and in particular to an antenna fixed in an electronic device for receiving or transmitting signals in two distinct frequency bands.
2. Description of the Prior Art
The development of wireless local area network (WLAN) technology has been attended by the development of devices operating under the IEEE 802.11b standard (in the 2.45 GHz band) and the IEEE 802.11a standard (in the 5.25 GHz band). These devices benefit from a multi-band antenna. U.S. Pat. No. 6,204,819 discloses a conventional multi-band antenna. The multi-band antenna includes a first and second conductive branches 42, 46, and is provided for use within wireless communications devices, such as radiotelephones. A first conductive branch 42 has first and second feeds 43, 44 extending therefrom that terminate at respectively a first and second micro-electromechanical systems (MEMS) switches S1, S2. The second conductive branch 46 is in adjacent, spaced-apart relationship with the first conductive branch 42. One end of the second conductive 46 branch terminates at a third MEMS switch S3 and the opposite end of the second conductive branch 46 is connected to the first conductive branch 42 via a fourth MEMS switch S4. The fourth MEMS switch S4 is configured to be selectively closed to electrically connect the first and second conductive branches 42, 46 such that the antenna radiates as a loop antenna in a first frequency band. The fourth switch S4 is also configured to open to electrically isolate the first and second conductive branches 42, 46 such that the antenna radiates as an inverted-F antenna in a second frequency band different from the first frequency band. However, the switches add manufacturing cost and complexity to the antenna. Furthermore, the three dimensional structure of the antenna occupies a large space, which is counter to the trend toward miniaturization of portable electronic devices.
Hence, an improved multi-band antenna is desired to overcome the above-mentioned disadvantages of the prior art.
A main object of the present invention is to provide a multi-band antenna occupying smaller space.
A multi-band antenna in accordance with the present invention comprises an insulative substrate, a conductive element disposed on the substrate, and a feeder cable connecting with the conductive element. The conductive element includes a ground portion, a radiating portion, a first connecting portion and a second connecting portion. The first and second connecting portions are adapted to connect the ground portion with the radiating portion. The radiating portion comprises a plurality of radiating segments connecting in turn and perpendicularly to each other. The feeder cable is a coaxial cable having an inner core conductor connecting with the radiating portion and a outer shield conductor connecting with the ground portion. The ground portion, a part of the radiating portion, the second connecting portion and the feeder cable form a loop antenna, which operates in a higher frequency band. The ground portion, the radiating portion, the first connecting portion and the feeder cable form a planar inverted-F antenna, which operates in a lower frequency band.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of a preferred embodiment when taken in conjunction with the accompanying drawings.